Habitat associations with topography and canopy structure of tree species in a tropical montane forest on Mount Kinabalu,Borneo

Habitat associations with topography and canopy structure of 42 abundant tree species were studied in a 2.74-ha plot of tropical montane forest on Mount Kinabalu, Borneo. Many of these species belong to the same higher taxa including eight families and four genera. Analysis of intraspecific spatial distributions for stems ≥ 10 cm diameter revealed that 28 species (including all six species of Fagaceae) showed aggregated distributions at the 100-m² and/or 400-m² scales, and that 20 species showed habitat associations with topography by torus-translation tests; 17 species showed both characteristics. Species' associations with the local canopy structure were characterized by crown position index (CPI), which was defined relative to neighbour trees. The CPI differed greatly among individual stems at 10–40 cm diameter, and 19 species showed significantly different frequencies of crowns exposed vertically versus those shaded beneath the canopy. Mean growth rates at 10–40 cm diameter and size distributions of species were not related to topographic associations, but were explained by the associations with canopy structure; species with more exposed crowns grew faster and had less positively skewed distributions. Diversity in habitat associations was manifest between two genera (Syzygium and Tristaniopsis) in the family Myrtaceae and among species in these genera, but was less evident in other families and two genera (Garcinia and Lithocarpus). This revised version was published online in June 2006 with corrections to the Cover Date.     

Elevational diversity patterns of small mammals on Mount Kinabalu, Sabah, Malaysia

1 Diversity patterns of small mammals were studied along an elevational transect on Mount Kinabalu, the highest mountain in South‐east Asia, utilizing data from previously existing sources and a new field study. A mark‐and‐release study (conducted during wet and dry seasons between November 1994 and April 1995) resulted in captures of 12 small mammal species, including two species of squirrels, two tree shrews, seven murid rodents and one gymnure. 2 Based on data compiled from this survey, museum specimens, and published and unpublished literature (analysed by locally weighted sums of squares and quadratic polynomial regressions), species richness of small mammals formed a middle elevation bulge, highest at about 1200–1400 m and declining at lower and higher elevations. Trapping during two seasons did not change the assessment of the pattern. 3 A cluster analysis of these data indicated that there are two elevationally associated faunas, one in the highlands and another in the lowlands. The transition between these two assemblages is at 1700–1800 m elevation. The lowland faunal assemblage has the highest number of species, with maximum species richness at about 1300 m for total small mammal species, about 1200 m for arboreal species and about 1400 m for terrestrial species. 4 The areas where much overlapping of species occurs are the elevations where climate and vegetation change rapidly from lowland to montane types. Tree species, gymnosperms, orchids and ferns showed a similar curvilinear pattern along the same elevational gradient, with maximum species richness at about 1400–1500 m. Temperature declined progressively with increasing elevation, but rainfall and humidity reached their highest levels at about 1700 m. 5 Maximum diversity of small mammals thus occurred at the elevation where a highland and a lowland assemblage overlapped, where several types of plants reached their maximum diversity, and where rainfall and humidity reached their maxima. Similar patterns have been documented for small mammals, plants, and climate at sites scattered in Indo‐Australia from Taiwan to New Guinea.     

Dynamics,productivity and species richness of tropical rainforests along elevational and edaphic gradients on Mount Kinabalu,Borneo

We studied the dynamics of nine tropical rainforests on Mount Kinabalu, Borneo, at four elevations (700, 1,700, 2,700 and 3,100 m) on various edaphic conditions for four 2-year periods over 8 years (1995–2003), and examined the relationships with above-ground productivity. Mean growth rate of stem diameter, basal area turnover rate and estimated recruitment rate (using growth rate and size distribution) correlated with productivity among the nine forests in all periods. These rates based on growth rates of surviving stems appeared to be good measures of stand turnover. However, observed recruitment rate and mortality (and turnover rate as mean of these rates) based on direct observation of recruits and deaths did not correlate with productivity in some periods. These rates may not be useful as measures of stand turnover given small sample size and short census interval because they were highly influenced by stochastic fluctuation. A severe drought associated with the 1997–1998 El Niño event inflated mortality and depressed mean growth rate, recruitment rate and basal area turnover rate, but had little effect on the correlations between these rates (except mortality) and productivity. Across broad elevational and edaphic gradients on Mount Kinabalu, forest turnover, productivity and species richness correlated with each other, but the causal interpretation is difficult given the different histories and species pools among forests at different elevations.     

Plant speciation on tropical mountains: Leptospermum (Myrtaceae) on Mount Kinabalu, Borneo

The genus Leptospermum (Mytaceae) is represented on Mount Kinabalu, Borneo, by L.flavescens (widespread on Malesian mountains and uplands) and L.recurvum (endemic to Mount Kinabalu). Analysis of the general morphology, leaf characters, leaf anatomy and flavonoid content of field collection, of both taxa at 1970–4000 m indicated that L.recuruum is a distinct species, most probably derived from L.flavescenS. L.recurvum individuals display a striking variation in leaf pubescence. Seedlings of. These plants grown under uniform conditions were not genetically variable (as seen in the uniformity of peroxidase and acid phosphatase isozymes).Variation that did occur was not correlated with altitude or any other identifiable ecological factors. The sporadic distribution of individuals producing non-viable seeds, probably an expression of genetic load, is another indication of a lack of genetic diversity. L.recurvum may have evolved from a population of L.flaurscens on Mount Kinabalu, most probably during the Pleistocene.     

Structure,composition and species diversity in an altitude-substrate matrix of rain forest tree communities on Mount Kinabalu,Borneo

We studied forest structure, composition and tree species diversity of eight plots in an environmental matrix of four altitudes (700, 1700, 2700 and 3100 m) and two types of geological substrates (ultrabasic and non-ultrabasic rocks) on Mount Kinabalu, Borneo. On both substrate series, forest stature, mean leaf area and tree species diversity (both 4.8 cm and 10 cm diameter at breast height [dbh]) decreased with altitude. The two forests on the different substrate series were similar at 700 m in structure, generic and familial composition and tree species diversity, but became dissimilar with increasing altitude. The decline in stature with altitude was steeper on the ultrabasic substrates than on the non-ultrabasic substrates, and tree species diversity was generally lower on ultrabasic substrates than on non-ultrabasic substrates at 1700 m. The forests on non-ultrabasic substrates at higher altitudes and those on ultrabasic substrates at the lower altitudes were similar in dbh versus tree height allometry, mean leaf area, and generic and familial composition at 1700 m. These contrasting patterns in forest structure and composition between the two substrate series suggested that altitudinal change was compressed on the ultrabasic substrates compared to the non-ultrabasic substrates. Tree species diversity was correlated with maximum tree height and estimated aboveground biomass, but was not with basal area, among the eight study sites. We suggest that forests with higher tree species diversity are characterized by greater biomass allocation to height growth relative to trunk diameter growth under more productive environment than forests with lower tree species diversity.     

Phosphorus and nitrogen resorption from different chemical fractions in senescing leaves of tropical tree species on Mount Kinabalu,Borneo

Nutrient resorption, a process by which plants degrade organic compounds and resorb their nutrients from senescing tissues, is a crucial plant function to increase growth and fitness in nutrient-poor environments. Tropical trees on phosphorus (P)-poor soils are particularly known to have high P-resorption efficiency (PRE, the percentage of P resorbed from senescing leaves before abscission per total P in green leaves). However, the biochemical mechanisms underlying this greater PRE remain unclear. In this study, we determined the P concentration in easily soluble, nucleic acid, lipid and residual fractions for green and senescent leaves of 22 tree species from three sites, which differed in P availability, on the lower flanks of Mt. Kinabalu, Borneo. PRE varied from 24 to 93% and was higher in species from the P-poor site. P-resorption rate was greatest from the lipid fraction, the nucleic acid fraction, and lowest in the easily soluble fraction and the residual fraction when all the species were pooled. For species with higher PRE, P-resorption rate of the residual fraction was relatively high and was comparable in magnitude to that of the other labile fractions. This suggests that tree species inhabiting P-poor environments increased PRE by improving the degradation of recalcitrant compounds. This study suggests that plants selectively degrade organic compounds depending on environmental conditions, which is a key mechanism underlying the variation of PRE.     

Elevational species richness patterns for vascular plants on Mount Kinabalu, Borneo

Aim  We quantify the elevational patterns of species richness for all vascular plants and some functional and taxonomic groups on a regional scale on a tropical mountain and discuss some possible causes for the observed patterns.
Location  Mount Kinabalu, Sabah, Borneo.
Methods  A data base containing elevational information on more than 28,000 specimens was analysed for vascular plant distribution, taking into account sampling effort. The total species richness pattern was estimated per 300-m elevational interval by rarefaction analyses. The same methods were also applied to quantify species richness patterns of trees, epiphytes, and ferns.
Results  Total species richness has a humped relationship with elevation, and a maximum species richness in the interval between 900 and 1200 m. For ferns and epiphytes the maximum species richness is found at slightly higher elevations, whereas tree species did not have a statistically significant peak in richness above the lowest interval analysed.
Main conclusions  For the first time a rigorous estimate of an elevational pattern in species richness of the whole vascular plant flora of a tropical mountain has been quantified. The pattern observed depends on the group studied. We discuss the differences between the groups and compare the results with previous studies of elevational patterns of species richness from other tropical areas. We also discuss the methods used to quantify the richness pattern and conclude that rarefaction gives an appropriate estimate of the species richness pattern.     

Effects of topography on tropical lower montane forests under different geological conditions on Mount Kinabalu,Borneo

Species composition and forest structure change with topography.However, mechanisms for topographical vegetation changes are still not wellunderstood, because a topographical gradient is a complex environmentalgradientinclusive of many factors. The foot of Mt. Kinabalu is covered with three typesof geological substrates, i.e. Quaternary and Tertiary sedimentary rocks andultrabasic (serpentine) rock. Quaternary and Tertiary sedimentaryrocks are different in site age, but controlled in primary minerals. Tertiarysedimentary and ultrabasic rocks are contrasting in primary minerals, but arecomparable in age. This setting provides an opportunity to examine thevegetation differentiation along topographical gradients that are contrastinginmajor-nutrient supply due to the difference in site age and parent rock.We established a total of nine study plots by choosing three topographicalunits(ridge, middle- and lower-slope) on each substrate inthe tropical lower montane forest. Pool size and supply of soil N and Pdecreased upslope on each substrate, and the magnitude of the reduction fromslope to ridge decreased in the order of Quaternary sedimentary > Tertiarysedimentary > ultrabasic rock. Between-substrate difference in soilnutrient condition was greater on the lower-slopes than the ridges.Maximum tree size decreased and stem density increased upslope on eachsubstrate. Detrended correspondence analysis demonstrated that speciescomposition also changed along topographical gradients on all substrates.However, the magnitude of topographical changes in forest structure and speciescomposition varied with substrate and decreased from Quaternary sedimentary>Tertiary sedimentary > ultrabasic rock. The greatest between-substratedifference in vegetation occurred on the lower-slopes. Accordingly, ourresults suggest that the magnitude of vegetation changes due to topographybecomes smaller with decreasing pool size and supply of nutrients.     

Influence of temperature and soil nitrogen and phosphorus availabilities on fine-root productivity in tropical rainforests on Mount Kinabalu,Borneo

We investigated how temperature and nutrient availability regulate fine-root productivity in nine tropical rainforest ecosystems on two altitudinal gradients with contrasting soil phosphorus (P) availabilities on Mount Kinabalu, Borneo. We measured the productivity and the nutrient contents of fine roots, and analyzed the relationships between fine-root parameters and environmental factors. The fine-root net primary productivity (NPP), total NPP, and ratio of fine-root NPP to total NPP differed greatly among the sites, ranging from 72 to 228 (g m^?2 year^?1), 281–2240 (g m^?2 year^?1), and 0.06–0.30, respectively. A multiple-regression analysis suggested a positive effect of P availability on total NPP, whereas fine-root NPP was positively correlated with mean annual temperature and with P and negatively correlated with N. The biomass and longevity of fine roots increased in response to the impoverishment of soil P. The carbon (C) to P ratio (C/P) of fine roots was significantly and positively correlated with the P-use efficiency of above-ground litter production, indicating that tropical rainforest trees dilute P in fine roots to maintain the C allocation ratio to these roots. We highlighted the mechanisms regulating the fine-root productivity of tropical rainforest ecosystems in relation to the magnitude of nutrient deficiency. The trees showed C-conservation mechanisms rather than C investment as responses to decreasing soil P availability, which demonstrates that the below-ground systems at these sites are strongly limited by P, similar to the above-ground systems.     

Soil phosphorus fractionation and phosphorus-use efficiencies of tropical rainforests along altitudinal gradients of Mount Kinabalu, Borneo

We studied soil phosphorus (P) fractionation and P-use efficiencies (PUEs) of rainforests along altitudinal gradients (700–3100 m) on two types of parental rocks (sedimentary versus ultrabasic) on Mount Kinabalu, Borneo. Sedimentary rocks were known to contain more quartz (which does not adsorb P) than ultrabasic rocks. The pool (top 30 cm) of total P was always greater on sedimentary (ranging from 34.9 to 72.6 g m^–2) than on ultrabasic (9.0–29.2 g m^–2) rocks at comparable altitudes. Accordingly, the pools of organic P and labile inorganic P were always greater on sedimentary than on ultrabasic rocks. The pool of primary mineral, calcium P increased upslope from 1.7 to 4.3 g m^–2 on sedimentary rock, suggesting that the altitudinal sequence of the sites reflected a decreasing magnitude of soil weathering upslope. The pool of calcium P on ultrabasic rock did not vary consistently with altitude (1.2–2.8 g m^–2), probably reflecting the greater between-site variability of primary mineral P in parent rocks. When all sites were compared, the pool of most labile, bicarbonate-extracted inorganic P increased (ranging from 0.02 to 1.85 g m^–2) with increasing calcium P. Calcium P was therefore considered to be an important P source to the biota on Kinabalu. Gross patterns in the variation of PUE (indexed as the reciprocal of the P concentration in litter) were best explained by the pool size of actively cycling P (total P minus occluded inorganic P). PUE, however, demonstrated distinct altitudinal patterns to generate an intricate conrol of P use pattern by soil P pools and altitude. Received: 2 August 1998 / Accepted: 28 November 1999     

Disentangling spatial,environmental and historical effects on tropical forest tree species turnover

空间、环境和历史因素对热带森林树种周转的影响本文通过回答以下问题来分析空间距离、当前和过去的环境差异及这几个因素对树木群落分类和系统发育转换的影响：(i)树木群落分类和系统发育转换是否与空间距离通过环境差异产生的间接影响相关？(ii)树木群落分类和系统发育转换是否随古气候(末次盛冰期和中全新世)的变化而变化？本文对巴西的14个大西洋雨林样点(采样面积20.4 ha) 83个科615个种进行了研究,获得了当前、中全新世和末次盛冰 期的地块地理坐标、土壤变量和样点生物气候变量。我们使用基于距离的结构方程模型(SEM)来(i)检测空间距离和环境差异的直接影响,以及(ii)检测空间距离通过环境差异对分类(Bray-Curtis距离)和系统发育转换(Comdist和Comdistnt距离)的间接影响。研究结果表明,空间距离通过环境差异对分类和系统发育转换的间接影响较弱。基于生态位中性的历史过程带来的直接影响驱动了树木群落的转换。因此,我们推断古气候(历史过程)促进了产生当前植物区系分支的选择,而空间距离(中性的过程)限制了物种从区域种库向外扩散的范围,环境条件(基于生态位的过程)则在本地选择能够持续生存的分类群。     

Studies in Garcinia, dioecious tropical forest trees: agamospermy

RICHARDS, A. J., 1990. Studies in Garcinia , dioecious tropical forest trees: agamospermy . In Garcinia , agamospermy is known or suspected for ten species. Most are facultative agamosperms, with males occurring, but males are probably lacking in G. mangostana . In G. mangostana and G. hombroniana , adventitious embryony occurs autonomously, and haploid parthenogenesis may also occur rarely. In G. parvifolia , it is reported previously that gametophytic agamospermy occurs, and adventitious embryos are suppressed. Autonomous endospermy is found in G. mangostana and G. parvifolia . In G. hombroniana , endosperm probably only develops after PEN fertilization. In G. hombroniana , some proembryos are formed precociously, and further proembryo formation is inhibited by sexual embryos. Asexual proembryos tend to occur in large ovules in small ovaries, and sexual embryos tend to occur in small ovules in large ovaries. It is considered that facultative agamospermy renders the genus Garcinia particularly suitable for the development of new types of fruit. Agamospermy in a dioecious genus, adventitious embryony in the absence of fertilization and/or pseudogamy, and the co-occurrence of gametophytic and sporophytic agamospermies in the same genus are unusual phenomena, which are discussed in the context of the lifestyle of a tropical forest tree. For G. hombroniana, n = 24, and for G. cowa, n = 26 are reported.     

Interactive influences of climate and parent material on soil microbial community structure in Bornean tropical forest ecosystems

Climate and parent material strongly control vegetation structure and function, yet their control over the belowground microbial community is poorly understood. We assessed variation in microbial lipid profiles in undisturbed forest soils (organic and surface mineral horizons) along an altitudinal gradient (700, 1,700, and 2,700 m a.s.l. mean annual temperature of 12–24°C) on two contrasting parent materials (acidic metasedimentary vs. ultrabasic igneous rock) in Mt. Kinabalu, Borneo. Soil organic carbon and nitrogen concentrations were generally higher at higher altitudes and, within a site, at upper soil horizons. Soil pH ranged from 3.9 to 5.3, with higher values for the ultrabasic soils especially at higher altitudes. The major shifts in microbial community structure observed were the decline in the ratio of fungal to bacterial lipid markers both with increasing soil depth and decreasing altitude. The positive correlation between this ratio with soil C and N concentrations suggested a strong substrate control in accord with the literature from mid to high-latitude ecosystems. Principal component analysis using seven groups of signature lipids suggested a significant altitude by parent material interaction—the significant difference in microbial community structure between the two rock types found at 2,700-m sites developed on weakly weathered soils diminished with decreasing altitude towards 700-m sites where soils were strongly weathered. These results are consistent with the hypothesis that parent material effect on soil microbial community (either directly via soil geochemistry or indirectly via floristic composition) is stronger at an earlier stage of ecosystem development.     

Relationships between landscape patterns and species richness of trees,shrubs and vines in a tropical forest

The present study aims to identify and characterize the relationships among landscape structure and plant diversity in a tropical landscape forest in Quintana Roo, Mexico. Total species richness as well as that of trees, shrubs and vines species were identified from 141 sampling quadrats (16,543 individuals sampled). Based on vegetation classes obtained from multi-spectral satellite image classification, I constructed plant diversity maps of the landscape under study using stratified kriging. I calculated the mean number of species in individual patches as the average values of kriging estimates inside of each patch. I then explored the relationships between landscape pattern metrics and the species richness of trees, shrubs and vines, as well as all groups combined using regression analysis. I employed Akaike Information Criterion (AIC) to select a set of candidate models. Based on akaike weights, I calculated model-averaged parameters. Results show that plant diversity of the patches depends on both the quality of the surrounding habitats and the proximity of surrounding patches (i.e., patch isolation).     

An altitudinal transect study of the vegetation on Mount Kinabalu,Borneo

A quantitative transect analysis of altitudinal sequences of forest canopy species from 600 to 3400 m asl on Mt. Kinabalu (4101 m), Borneo, resulted in four discrete altitudinal vegetation zones. These were made up of mutually exclusive species groups for lowland (<1200 m asl), lower montane (1200 to 2000–2350 m asl), upper montane (2000–2350 to 2800 m asl), and subalpine (2800 to the forest line, 3400 m asl) zones. Zonal soil types were correlated with the vegetation zones. In upslope sequence, these were: lowland Oxisols, montane Histosol/Spodosol complex, and subalpine Inceptisols. The highest contents of organic carbon, extractable phosphorus, and exchangeable magnesium and potassium were recorded in the lower and upper montane zones. The upper boundaries of the lowland, upper montane and subalpine zones coincided with thermal thresholds of latitudinal bioclimatic zones: 18°C TMIN (Köppen's tropical), WI 85 (Kira's warm temperate), and WI 45 (Kira's cool temperate), respectively. The upper limit of the lower montane zone was correlated with an abrupt increase of water surplus estimated from the annual rainfall minus annual potential evaporation. These climatic characteristics appear to define ecological altitudinal turnover points, so called critical altitudes, where groups of associated species are displaced by other groups.Abbreviations asl = above sea level - DBH = diameter at breast height - PHQ = Park headquarters - TMAX = Mean daily maximum air temperature - TMIN = Mean daily minimum air temperature - TWINSPAN = Two-way indicator species analysis - WI = Warmth index